Closed #3116: fixed xxxRGBAs' four bugs at setCascadeColorEnabled/setCascadeOpacityEnabled functions

fixed xxxRGBAs' four bugs at setCascadeColorEnabled/setCascadeOpacityEnabled functions:
1. if developers set the parent xxxRBGA object's _cascadeOpacityEnabled/_cascadeColorEnabled first, then set the color/opacity to some value, finally add a child node to this xxxRBGA object through addChild function, but these added children's color/opacity doesn't affected by the parent node.
2. A child Sprite's color/opacity doesn't affected by its parent node when the child sprite calls setColor/setOpacity and its parent node's _cascadeOpacityEnabled/_cascadeColorEnabled is true. 
3. The LabelTTF doesn't work when calls setCascadeColorEnabled/setCascadeOpacityEnabled.
4. The LayerGradient doesn't work when calls setCascadeColorEnabled/setCascadeOpacityEnabled.